EnDat supports the use of encoders in safety-related applications. This capability is based on the following standards: DIN EN ISO 13849-1 (successor to EN 954-1), as well as EN 61508 and EN 61800-5-2.
In these standards, safety-related systems are assessed based on the failure probabilities of integrated components and subsystems, among other criteria. This modular approach helps manufacturers implement their complete systems by allowing them to build upon previously qualified subsystems.
The functional safety provided with EnDat 3 encoders for applications up to SIL 3 is based on the following factors:
- Position value
- Two independent position values: Pos1 (high resolution) and Pos2 (low resolution, if applicable)
- Comparison of Pos1 and Pos2 by the safe control unit
- Forced dynamic sampling
- Cyclic testing of the monitoring function in the encoder
- Error messages
- Monitoring of error bits F1 and F2
- Due to the black channel, a safe EnDat master is not required and is therefore not part of the safety chain.
- Separation of communication to the motion controller and safe control unit (e.g., separate error messages)
To sum up:
Convenient implementation is possible thanks to the black-channel approach combined with standardized position data formats and the option of relocating forced dynamic sampling to the encoder.